In various orthopedic surgical procedures, it is necessary to secure portions of a spinal column in a relatively fixed relationship. This need is often a result of disease, damage or congenital deformation. For example, when one or more intervertebral disks of the spine degenerates due to trauma or disease, the spinal cord or emergent nerve can become compressed. This condition results in chronic and sometimes debilitating, neck, back, or peripheral pain.
One method of treatment for intervertebral disk degeneration involves surgical decompression of nerves, discectomy, and interbody fusion. Interbody fusion involves reestablishment of the normal gap between adjacent vertebral bodies. Heretofore, surgeons have employed various types of artificial implants and prostheses to stabilize the spinal column and promote fusion. The gap between adjacent vertebral bodies is commonly spanned with rigid spacer that is filled with bone graft material to facilitate bony fusion of the two vertebral bodies. A successful fusion stabilizes the spine, reduces pressure on the spinal cord and nerve roots, and reduces or eliminates back pain.
It is also known to insert harvested bone grafts or implants between adjacent vertebral bodies to maintain a normal gap. Such allografts comprise biological materials that are replaced over time with the patient's own bone through bone ingrowth. One common implant is referred to as a Cloward dowel. Cloward dowels are circular grafts made from autologous illiac crest bone. The dowels are bicortical, having porous cancellous bone between two cortical surfaces. A cylindrical cutting tool is typically used to prepare the cervical site to receive the dowel.
More recently, fibular and humeral cortical rings have been used as interbody spacers for spinal fusions such as anterior cervical fusions. Several tissue banks conventionally offer pre-shaped allograft cortical rings for this purpose.
While known devices for spinal fixation have proven to be effective in various applications to support the spinal column and promote fusion, they nevertheless can be the subject of certain improvements.